The subject matter disclosed herein relates generally to imaging techniques and, more particularly, to systems and methods for performing iterative multi-material correction of image data.
Non-invasive imaging technologies enable images of the internal structures or features of a patient to be obtained without performing an invasive procedure on the patient. In particular, such non-invasive imaging technologies rely on various physical principles, such as the differential transmission of X-rays through the target volume or the reflection of acoustic waves, to acquire data and to construct images or otherwise represent the observed internal features of the patient.
For example, in computed tomography (CT) and other X-ray based imaging technologies, X-ray radiation spans a subject of interest, such as a human patient, and a portion of the radiation impacts a detector where the image data is collected. In digital X-ray systems, a photodetector produces signals representative of the amount or intensity of radiation impacting discrete pixel regions of a detector surface. The signals may then be processed to generate an image that may be displayed for review. In CT systems, a detector array, including a series of detector elements, produces similar signals through various positions as a gantry is displaced around a patient.
In the images produced by such systems, it may be possible to identify and examine the internal structures and organs within a patient's body. However, the produced images may also include artifacts that adversely affect the quality of the images due to a variety of factors. For example, these factors may include beam hardening for non-water materials, heel-effect related spectral variation in wide cone CT systems, bone induced spectral (BIS) due to detection variation of different detector pixels coupled to spectral changes attenuated by bone or other non-water materials, and other factors. Accordingly, a variety of techniques have been developed to attempt to correct for these artifacts.
For example, multi material correction (MMC) is an algorithm developed for spectral calibration (i.e., beam hardening correction (BHC)) for wide-cone CT. However, a key assumption in MMC is that the re-projection of iodine in the first-pass CT images approximates the polychromatic projection of iodine after water BHC. MMC is therefore typically limited to a one-step correction procedure, thus limiting the extent to which beam hardening effects can be corrected and requiring post-processing parameter tuning. Accordingly, there exists a need for systems and methods that address these drawbacks.